Media Encoder CC rendering issues

Since upgrading to Media Encoder CC 2018 a few days ago I am having major problems rendering files I could render perfectly before the upgrade. These are simple compositions created in After Effects (also upgraded at the same time). They are only 10 to 15 seconds long, use no plugins or special effects.

Before upgrading they would render from Media Encoder in a matter of seconds / minutes, and the rendering would start immediately. Since upgrading they frequently take 5 minutes to begin rendering, often complete but with errors, and more often than not I get a 'Cannot read from source' error, or Media Encoder just hangs and nothing happens. The files work fine and play perfectly in After Effects, and will render with no issues or errors from there. Prior to updating the software a few days ago I never had this issue.

Changing the renderer - Mercury Playback Engine GPU Acceleration (OpenCL) / (Metal) / Software only - makes no difference.

I'm using a MacBook Pro (Retina, 15-inch, Mid 2014)
Processor: 2.5 GHz Intel Core i7

Memory: 16 GB 1600 MHz DDR3

Graphics: NVIDIA GeForce GT 750M 2048 MB

Intel Iris Pro 1536 MB

Adobe Media Encoder CC Version 12.0 (Build 202)

Adobe After Effects CC Version 15.0.0 (Build 180)

From Error Log:

- Source File: ###

- Output File: ###

- Preset Used: ### Instore Screens

- Video:

- Audio:

- Bitrate:

- Encoding Time: 00:00:00

12/05/2017 03:41:09 PM : Encoding Failed

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Could not read from the source. Please check if it has moved or been deleted.

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